Human monocytes from normal subjects and persons with Gaucher's disease will be grown in a newly devised in vitro culture system. Estimations of the glucocerebroside content of the culture cells will be made at intervals. If accumulation of glycolipid can be demonstrated to occur in these cells they will be "fed" red cells loaded with purified human glucocerebrosidase and the effect of this feeding on glucocerebroside levels will be measured. If the glucocerebroside level of such monocytes does not increase spontaneously, they will be "fed" resealed red cell membranes loaded with glucocerebroside and this will be followed by administration of glucocerebrosidase.